Commit 70f008fb authored by Amelie Delaunay's avatar Amelie Delaunay Committed by Vinod Koul
Browse files

dmaengine: dmatest: prevent using swiotlb buffer with nobounce parameter 



Source and destination data buffers are allocated with GPF_KERNEL flag.
It means that, if the DDR is more than 2GB, buffers can be allocated above
the 32-bit addressable space. In this case, and if the dma controller is
only 32-bit compatible, swiotlb bounce buffer, located in the 32-bit
addressable space, is used and introduces a memcpy.

To prevent this extra memcpy, due to swiotlb bounce buffer use because
source or destination data buffer is allocated above the 32-bit addressable
space, force source and destination data buffers allocation with GPF_DMA
instead, when nobounce parameter is true.

Signed-off-by: default avatarAmelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20231124160235.2459326-1-amelie.delaunay@foss.st.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 25b63622

drivers/dma/dmatest.c

+16 −1
Original line number Diff line number Diff line
@@ -21,6 +21,10 @@ 
#include <linux/slab.h>

#include <linux/wait.h>



static bool nobounce;

module_param(nobounce, bool, 0644);

MODULE_PARM_DESC(nobounce, "Prevent using swiotlb buffer (default: use swiotlb buffer)");



static unsigned int test_buf_size = 16384;

module_param(test_buf_size, uint, 0644);

MODULE_PARM_DESC(test_buf_size, "Size of the memcpy test buffer");
@@ -90,6 +94,7 @@ MODULE_PARM_DESC(polled, "Use polling for completion instead of interrupts"); 


/**

 * struct dmatest_params - test parameters.

 * @nobounce:		prevent using swiotlb buffer

 * @buf_size:		size of the memcpy test buffer

 * @channel:		bus ID of the channel to test

 * @device:		bus ID of the DMA Engine to test
@@ -106,6 +111,7 @@ MODULE_PARM_DESC(polled, "Use polling for completion instead of interrupts"); 
 * @polled:		use polling for completion instead of interrupts

 */

struct dmatest_params {

	bool		nobounce;

	unsigned int	buf_size;

	char		channel[20];

	char		device[32];
@@ -215,6 +221,7 @@ struct dmatest_done { 
struct dmatest_data {

	u8		**raw;

	u8		**aligned;

	gfp_t		gfp_flags;

	unsigned int	cnt;

	unsigned int	off;

};
@@ -533,7 +540,7 @@ static int dmatest_alloc_test_data(struct dmatest_data *d, 
		goto err;



	for (i = 0; i < d->cnt; i++) {

		d->raw[i] = kmalloc(buf_size + align, GFP_KERNEL);

		d->raw[i] = kmalloc(buf_size + align, d->gfp_flags);

		if (!d->raw[i])

			goto err;
@@ -655,6 +662,13 @@ static int dmatest_func(void *data) 
		goto err_free_coefs;

	}



	src->gfp_flags = GFP_KERNEL;

	dst->gfp_flags = GFP_KERNEL;

	if (params->nobounce) {

		src->gfp_flags = GFP_DMA;

		dst->gfp_flags = GFP_DMA;

	}



	if (dmatest_alloc_test_data(src, buf_size, align) < 0)

		goto err_free_coefs;
@@ -1093,6 +1107,7 @@ static void add_threaded_test(struct dmatest_info *info) 
	struct dmatest_params *params = &info->params;



	/* Copy test parameters */

	params->nobounce = nobounce;

	params->buf_size = test_buf_size;

	strscpy(params->channel, strim(test_channel), sizeof(params->channel));

	strscpy(params->device, strim(test_device), sizeof(params->device));